block: Adjust elv_iosched_show to return "none" for bio-based DM

Bio-based DM doesn't use an elevator (queue is !blk_queue_stackable()).

Longer-term DM will not allocate an elevator for bio-based DM.  But even
then there will be small potential for an elevator to be allocated for
a request-based DM table only to have a bio-based table be loaded in the
end.

Displaying "none" for bio-based DM will help avoid user confusion.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 6df2b5056b51..0abce473d606 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -1097,7 +1097,7 @@ ssize_t elv_iosched_show(struct request_queue *q, char *name)
         struct elevator_type *__e;
         int len = 0;
 
-        if (!q->elevator)
+        if (!q->elevator || !blk_queue_stackable(q))
                 return sprintf(name, "none\n");
 
         elv = e->elevator_type;